As EUV lithography is on its way into production stage, studies of optics contamination and cleaning under realistic
conditions become more and more important. Due to this fact an Exposure Test Stand (ETS) has been constructed at
XTREME technologies GmbH in collaboration with Fraunhofer IOF and with financial support of Intel Corporation.
This test stand is equipped with a pulsed DPP source and allows for the simultaneous exposure of several samples. In the
standard set-up four samples with an exposed area larger than 35 mm2 per sample can be exposed at a homogeneous
intensity of 0.25 mW/mm2. A recent update of the ETS allows for simultaneous exposures of two samples with
intensities up to 1.0 mW/mm2. The first application of this alternative set-up was a comparative study of carbon
contamination rates induced by EUV radiation from the pulsed source with contamination rates induced by quasicontinuous
synchrotron radiation. A modified gas-inlet system allows for the introduction of a second gas to the
exposure chamber. This possibility was applied to investigate the efficiency of EUV-induced cleaning with different gas
mixtures. In particular the enhancement of EUV-induced cleaning by addition of a second gas to the cleaning gas was
studied.